A variety of guidance systems are used in military applications. As one example, semi-active laser (SAL) designation is used in military systems to designate targets and guide a missile or other weapon to the target. In a typical SAL system, the operator of a SAL designator fires a narrow pulsed laser beam at a target. The SAL designator may be man-portable or carried by a designator aircraft such as an unmanned aerial vehicle (UAV).
The laser beam fired by the SAL designator reflects off the target to provide a reflected spot that can be detected by a SAL sensing system. When the designated target is within range, the SAL sensing system processes the detected reflection to detect the spot, acquire the designated target, and verify that the SAL designator was the source. The SAL sensing system includes processing equipment for generating guidance commands from the pulse-stream to guide the weapon to impact.
The SAL system thus provides the ability to precisely guide weapons to a designated target. Furthermore, the SAL system provides a “man-in-the-loop” capability that is preferred in many battlefield situations.
One issue in SAL systems is the wavelength (and thus frequency) of the laser beam used to designate targets. In current implementations, SAL designators have been limited to wavelengths that are not desirable for all applications. For example, typical SAL systems are limited to a single passband, and do not support more than one laser designator wavelength.
Thus, there remains a continuing need for SAL systems in general, and SAL sensing systems in particular that can be adapted to use different electromagnetic radiation wavelengths.